Rail-distance-traveled estimates are typically based on a tachometer approach or via GPS, but such systems do not provide sufficient accuracy. Doppler radar and pulse generator systems are more accurate but have environmental problems in extreme conditions. Laser based systems must have an optically clear path to the reflecting surface, and reduced visibility due to snow accumulation or similar conditions are problematic challenges to accurate measurement. Measurement techniques relying on wheel rotation are also known, but these techniques suffer from error due to wheel slippage, wheel wear, and a number of other factors.
What is needed is a distance-traveled measurement system that can be installed on any railroad car, that is accurate and reliable in any weather conditions, and that is accurate to with 5 ft/mile.